1. Field of the Invention
This invention relates to a treatment system having a gate device for a decompression chamber and, more particularly, it relates to a magnetron plasma etching apparatus, having a load-lock gate, used for treating ultra LSIs.
2. Description of the Related Art
An installation for manufacturing semiconductor devices normally comprises various apparatuses for processing semiconductor wafers in vacuum, where load-lock gate devices are applied to partition connected vacuum chambers or isolate the inside of vacuum chambers from atmosphere so as to treat wafers continuously. A toggled gate device is a type of these gate devices.
A toggled gate device is so designed that it moves and aligns a gate with a gate aperture by means of rotatable gate rollers that come to abut or rather collide with the forward end of the gate. After the collision, the force that tends to drive the gate further in that direction is utilized to bring the gate in close contact with the gate aperture to make a seal as the rollers are rotated on the gate.
The rollers that take part in the collision are normally made of stainless steel, whereas the gate including its upper portions that also take part in the collision is usually made of aluminum. Since the collision takes place under considerable pressure and, thereafter, the rollers are forced to rotate on the surface of the gate under that pressure, the upper portions of the gate against which the rollers are respectively pressed are scraped to produce dust that can be dispersed into and pollute the ambient atmosphere of the processing site.
The process of manufacturing semiconductor devices, such as devices having an integration degree of more than 16M, requires accurate treatment. In a magnetron plasma etching apparatus that requires a high degree of vacuum and performs anisotropic etching for semiconductor devices of more than 16M, the process can be seriously affected by the dust given off by scraping the metal gate in terms of yield and efficiency. Such dust did not cause problems when the etching apparatus was used for treating semiconductor devices of less than 16M.
Besides, as the surface of the metal gate is scraped by the rollers, the toggled gate device tends to malfunction and adversely affect its reliability.
Additionally, a gate device applied to a load-lock type vacuum chamber connected to a magnetron plasma etching apparatus can be selectively eroded by the air in the etching apparatus at the scraped area.
While the above described problems are particularly remarkable at the portions of the gate against which the respective rollers collide, similar problems may be observed at other locations where friction takes place.